The purpose of this study is to establish the mechanism(s) of progression of communicating syringomyelia. Communicating syringomyelia usually accompanies abnormalities at the craniocervical junction. Measurement of intraventricular pressure, intrathecal pressure, and intrasyrinx pressure should provide data which elucidate the hydrodynamic mechanism(s) of progression of syringomyelia. Radiographic testing, including MRI flow studies, ultrasonography, and Imatron CT, will demonstrate how pathologic anatomy alters normal cerebrospinal fluid (CSF) flow. The effect of posterior fossa craniectomy, upper cervical laminectomy, and duraplasty on CSF flow, syrinx size, and neurologic function will be evaluated. One patient has been treated to date. The pressure measurements were performed without complication. CSF circulation at the foramen magnum improved with surgery in this patient. The syrinx decreased in size following surgery We plan to proceed with an additional nine patients.